Among various internal combustion engines to be mounted on a vehicle, there is one which has a clutch mechanism which is coupled when engine speed exceeds a coupling engine speed. Similarly, among various devices for injecting fuel to an internal combustion engine of the type mentioned above, there is one which includes a starting time engine speed control device for controlling fuel to be injected by correcting an amount thereof, with respect to a basic fuel injection control, within a predetermined period of time from the start of the internal combustion engine by means of starting time fuel injection control.
One starting time engine speed control device of the type mentioned above is disclosed in Japanese Patent Early Laid-open Publication No. Hei 2-30940. In the device disclosed by this publication, when fuel is injected in an increased amount decided in accordance with a cooling temperature at the starting time of an internal combustion engine, if engine speed is increased at the starting time of the internal combustion engine, fuel is injected by decreasingly correcting the amount of fuel in accordance with engine speed, and if engine speed is decreased at the starting time of the internal combustion engine, the increasing correction of the amount of fuel is prohibited.
It sometimes happens that engine speed is meaninglessly increased in spite of the fact that the throttle valve is in an idle position, when fuel to be injected is controlled such that an amount thereof is corrected, with respect to a basic fuel injection control, within a predetermined period of time from the starting time of the internal combustion engine by means of a starting time fuel injection control.
In the event as mentioned above, it sometimes gives rise to a problem that in the aforementioned internal combustion engine which is mounted on a vehicle and which has a clutch mechanism which is coupled when engine speed exceeds a coupling engine speed, the clutch is coupled when the increasing engine speed has exceeded the coupling engine speed, and as a result, a driving force of the internal combustion engine is transmitted to a driving mechanism. Furthermore, it sometimes gives rise to another problem that the clutch mechanism is coupled when the engine speed is increased exceeding the coupling engine speed by a drivers adjustment of an idle adjusting screw of the internal combustion engine in order to set the idle speed to an increased level, with the result that a driving force of the internal combustion engine is transmitted to the driving mechanism.
Therefore, it can be considered that by controlling fuel to be injected in such a manner as to increasingly correct an amount thereof by means of starting time fuel injection control in accordance with an increasing engine speed up to a coupling engine speed when fuel is injected by correcting the amount thereof by means of a starting time fuel injection control, the air-fuel ratio is intensified to reduce engine output and to lower the engine speed thereby preventing coupling of the clutch mechanism.
When fuel to be injected is controlled by gradually increasingly correcting an amount thereof at the starting time of an internal combustion engine as mentioned above, removal of this correction of engine speed is managed by time correction. Therefore, the gradual increasing correction of the amount of fuel by means of the engine speed correction is continued until the passage of a preset time which has been preset by the time correction.
Such being the case, when a driver attempts to drive a vehicle immediately after the start of the internal combustion engine, the driver encounters inconveniences in that the air-fuel ratio becomes improper due to intensified air-fuel ratio in the speed area of the gradual increasing correction of the amount of fuel, and the engine output is reduced to prevent increase of the engine speed, with the result that the vehicle drives awkwardly.
The above-mentioned awkward driving state is disadvantageous for vehicles of the type which are required to start driving, immediately after the start of the internal combustion engine, such as snowmobiles, etc.
It is therefore a first object of the present invention to provide a starting time engine speed control device for an engine having a clutch mechanism which is coupled when engine speed exceeds a coupling engine speed capable of preventing a meaningless increase of engine speed when fuel to be injected is controlled by correcting an amount thereof, with respect to a basic fuel injection control, by means of starting time fuel injection control.
A second object of the present invention is to realize a starting time engine speed control device capable of obviating awkward driving states due to improper air-fuel ratio when the vehicle is immediately started after the start of the internal combustion engine.
In order to achieve the first object, the present invention is characterized by a starting time engine speed control device for controlling fuel to be injected by correcting an amount thereof, with respect to a basic fuel injection control, within a predetermined period of time after the start of engine by means of starting time fuel injection control, wherein said starting time engine speed control device includes control means adapted to control the fuel to be injected by gradually increasingly correcting the amount thereof in accordance with increasing engine speed up to said coupling engine speed.
Similarly, in order to achieve the second object, the present invention is characterized by a starting
speed control device for controlling fuel to be injected by correcting an amount thereof, with respect to a basic fuel injection control, within a predetermined period of time after the start of engine by means of starting time fuel injection control, wherein said starting time engine speed control device includes control means adapted to control the fuel to be injected by gradually increasingly correcting the amount thereof in accordance with an increasing state of the engine speed up to said coupling engine speed, said control means being further able to control such that when a throttle opening degree is equal to or more than a preset throttle opening degree and engine speed is equal to or higher than a preset level, the mode of controlling is shifted from said starting time fuel injection control to said basic fuel injection control and said amount of fuel decided by said basic fuel injection control is injected.
According to one embodiment of the invention, by letting the control means control fuel to be injected in such a manner as to increasingly correct an amount thereof by means of starting time fuel injection control in accordance with increasing engine speed up to the coupling engine speed, the air-fuel ratio is intensified to reduce engine output and to lower the engine speed thereby prohibiting coupling of the clutch mechanism.
According to another embodiment, by letting the control means control such that when the throttle valve is opened to the extent equal to or more than a preset throttle opening degree and the engine speed is at a level equal to or higher than a preset engine speed, the vehicle can start driving immediately after the start of the internal combustion engine, because the mode of controlling is shifted from the starting time fuel injection control to the basic fuel injection control and there can be obtained an engine output required for a driving of the vehicle by a proper air-fuel ratio, by injecting the amount of fuel decided by this basic fuel injection control.